On the role of Zr substitution in structure modification and photoluminescence of Li5+2xLa3(Ta1−xZrx)2O12:Eu garnet phosphors. Issue 9 (17th February 2021)

• Record Type: Journal Article
• Authors: Du, Panpan; Li, Siyuan; Wang, Xuejiao; Zhu, Qi; Li, Ji-Guang
• Is Part Of: Dalton transactions. Volume 50:Issue 9(2021)
• Page Start: 3337
• Page End: 3347
• Publication Date: 2021-02-17
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/d0dt04245e
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The role of Zr substitution in structure modification for a series of garnet-type Li5+2 x La3 (Ta1− x Zr x )2 O12 :Eu phosphors was identified, with which the observed luminescence behaviors of Eu 3+ were successfully deciphered. Abstract : Solid-state reaction at 1000 °C produces a series of Li-stuffed Li5+2 x (La1− y Eu y )3 (Ta1− x Zr x )2 O12 garnet phosphors ( x = 0–1, y = 0.05–0.6) that exhibit favorable efficiency and thermal stability for red luminescence under either blue or n-UV light excitation, where the optimal composition was identified to be x = 0.5 and y = 0.4. The concentration quenching of luminescence was determined to occur via electric dipole–dipole interactions. Zr 4+ substitution for Ta 5+, accompanied by additional Li + for charge compensation, was found via Rietveld structure refinement and Raman/UV-Vis spectroscopy to profoundly affect the tetrahedral and octahedral occupancies of Li, the symmetry of (La/Eu)O8 dodecahedron, and the bandgap of the host lattice and cation disorder, with which the systematically varying excitation and emission behaviors of Eu 3+ were deciphered. The Li6 (La0.6 Eu0.4 )3 (Ta0.5 Zr0.5 )2 O12 optimal phosphor showed quantum yields of ∼40 and 48% under 393 and 463 nm excitations, respectively, a fluorescence lifetime of ∼0.66 ms for its main emission at 610 nm, color coordinates of around (0.653, 0.347), and can retain as high as ∼85% of its room-temperature emission intensity at 423 K. The phosphor also exhibited a favorable performance for n-UV excited LED lighting.